Semiconductor manufacturing processing techniques are widely known, and include, among others, deposition of selected materials on a semiconductor wafer by epitaxial growth or other such techniques, both similar and diverse, for example molecular beam or ion-beam deposition. The so called "wafer" is commonly employed for formation thereon of either a singular sample, or a plurality of samples, each consisting of an arrangement of many components. Monitoring of a selected characteristic of the semiconductor wafer during the deposition process is of paramount importance so as to achieve quality devices without undue rejections or scrap. Examples of such selected characteristics are, among others, sheet resistivity and carrier lifetime.
Desirably, any monitoring of the semiconductors during the deposition process should be conducted if possible by a non-contact or non-destructive measurement technique or method that does not risk contaminating or damaging the semiconductor wafer. An example of such a technique is the use of microwaves to measure selected semiconductor properties or characteristics as particularly described in U.S. Pat. No. 5,103,182, entitled, "Electromagnetic Wave Measurement of Conductive Layers of a Semiconductor Wafer During Processing Fabrication In a Fabrication Chamber", issued to Moselehi. As described in the aforesaid patent, a microwave emitter and a microwave collector are employed within the confines of a semiconductor fabrication chamber. A microwave source, external to the semiconductor fabrication chamber, is coupled to the microwave emitter within the fabrication chamber. The microwave emitter is directed to impinge on the surface of a wafer in-process. In turn, microwave energy is reflected from the surface of the wafer and detected by the microwave collector waveguide thereby producing an output signal indicative of a selected characteristic of the wafer in-process.
Still another example is U.S. Pat. No. 5,451,886, entitled, "Method Of Evaluating Lifetime Of Semiconductor Material And Apparatus For The Same, issued to Ogita, et al, where a light source is employed to radiate a wafer surface, and a millimeter to submilimeter waveguide is used to supply the surface of the wafer with an electromagnetic wave generated by an oscillator, and for guiding a reflected wave from the surface thereof to a reflected wave detector.
Yet still another example is U.S. Pat. No. 5,430,386, entitled, "Method And Apparatus For Evaluating Semiconductor Wafer By Irradiation With Microwave And Excitation Light, issued to Morin, et al, where a light source is employed to radiate a wafer surface at the same time that microwaves are directed toward the surface and reflected therefrom. In turn, reflected microwave energy is detected to determine carrier lifetime.
Other examples include, among others, U.S. Pat. No. 5,142,224, entitled, "Non-Destructive Semiconductor Wafer Probing System Using Laser Pulses To Generate And Detect Millimeter Wave Signals", issued to Smith, et. al., where electrical signals are induced into the wafer for subsequent signal measurements indicative of the quality of the wafer; U.S. Pat. No. 5,228,776, entitled, "Apparatus For Evaluating Thermal And Electrical Characteristics In A Sample", issued to Smith, et al, where a modulated pump beam of radiation is employed for detecting characteristics of a semiconductor sample; and U.S. Pat. No. 4,842,686, entitled, "Wafer Processing Apparatus And Method", issued to Davios, et al, where ultraviolet radiation is generated with the semiconductor fabrication chamber by generating a plasma therein but remote from the face of the wafer.
Prior art systems similar to those described above are generally complex systems which are complex in design and not generally versatile to accommodate various fabrication conditions and requirements. Specifically, they cannot be used during fabrication.
However, a novel method and apparatus for monitoring sheet resistivity of a semiconductor substrate has been disclosed in a co-pending patent application, having Ser. No. 08/794,221, entitled, "Non-Destructive Method and Apparatus for Monitoring a Selected Semiconductor Characteristic of a Semiconductor Sample During Fabrication, in the name of Vladimir Sokolov, one of the applicants of the present inventions, and filed on even date herewith. There disclosed is a fabrication chamber modified to include quartz like windows or viewports. An mm-wave is generated outside a fabrication chamber and directed to pass through the viewport to impinge upon a wafer substrate during the fabrication process. In turn, a reflected mm-wave is detected by apparatus outside the fabrication chamber, signal processed, and a resistivity measurement is obtained.